The present invention relates to a contact for a vacuum interrupter and a vacuum interrupter using the contact.
For the purpose of improving an interruption performance or breaking capacity of the vacuum interrupter, it is required that arc is uniformly developed between the entire surfaces of electrodes without being concentrated onto local areas of the electrode surfaces upon power interruption. A vacuum interrupter of an axial magnetic field application type has been adopted to receive arc by the entire surfaces of the electrodes. The vacuum interrupter of such a type as described above produces an axial magnetic field between electrodes in the axial direction thereof during interruption. Owing to the production of the axial magnetic field, the developed arc is confined by the axial magnetic field so that loss of charged particles in an arc column can be reduced. This makes the arc stable and suppresses temperature rise at the electrodes, serving for improving the interruption performance.
U.S. Pat. No. 4,620,074 (corresponding to Japanese Patent Application Second Publication No. 3-59531) discloses a contact arrangement for vacuum switches. The arrangement includes two opposed cup-type contacts having hollow cylindrical contact carriers. Each contact carrier has a contact plate on the end surface thereof and a plurality of slots on the circumferential surface thereof. The slots are inclined with respect to a center axis of each contact carrier. The axial length (cup depth) of the contact carrier, the number of slots, the azimuth angle of the slots relative to an outer diameter of the contact carrier are specified.
For the purpose of obtaining the interruption performance of the vacuum interrupter at high voltage and large current, both of the diameter of the contacts and the gap (dissociation distance) between the contacts must be increased. In the above-described related art, if the diameter of the contacts and the gap therebetween are increased, a magnetic flux density between the electrodes will decrease to cause unstable arc between the electrodes so that the interruption operation will fail. In addition, if the azimuth angle of the slots of the contact carriers is set large in order to ensure the magnetic field generated between the electrodes, the contacts will be deteriorated in strength to cause deformation due to application of the force upon the switching on and off operation of the vacuum interrupter. This leads to deterioration in withstand voltage performance and interruption performance of the vacuum interrupter.
It would threrefore be desirable to provide a contact for a vacuum interrupter which is enhanced in magnetic field intensity without being deteriorated in mechanical strength. Further, it would be desirable to provide a vacuum interrupter using the contact, which can provide uniform distribution of the arc generated upon interruption and attain high interruption performance without increasing the size.
In one aspect of the present invention, there is provided a contact for a vacuum interrupter, comprising:
a hollow cylindrical contact carrier including a center axis, opposed axial end faces and an axial length extending along the center axis;
a contact plate disposed on one of the opposed axial end faces of the contact carrier;
a plurality of first slits extending from the one of the opposed axial end faces of the contact carrier and inclined with respect to the center axis of the contact carrier, the first slits having a first height x extending in the axial direction of the contact carrier; and
a plurality of second slits extending from the other of the axial end faces of the contact carrier and inclined with respect to the center axis of the contact carrier, the second slits having a second height y extending in the axial direction of the contact carrier, the second slits cooperating with the first slits to define a coil portion in the contact carrier therebetween which allows a current to flow and form an axial magnetic field along the axial direction of the contact carrier,
wherein assuming that the axial length of the contact carrier is 1, the first height x and the second height y satisfies a relationship given by the following expressions (1)-(3):
0.9xe2x89xa7xxe2x80x83xe2x80x83(1) 
xxe2x89xa7yxe2x89xa70.2xxe2x80x83xe2x80x83(2) 
1.4xe2x89xa7x+yxe2x89xa70.8xe2x80x83xe2x80x83(3) 
In a further aspect of the present invention, there is provided a A vacuum interrupter, comprising:
a vacuum envelope; and
a pair of contacts arranged coaxially and relatively moveably in the axial direction within the vacuum envelope,
each of the contacts comprising:
a hollow cylindrical contact carrier including a center axis, opposed axial end faces and an axial length extending along the center axis;
a contact plate disposed on one of the opposed axial end faces of the contact carrier;
a plurality of first slits extending from the one of the opposed axial end faces of the contact carrier and inclined with respect to the center axis of the contact carrier, the first slits having a first height x extending in the axial direction of the contact carrier; and
a plurality of second slits extending from the other of the axial end faces of the contact carrier and inclined with respect to the center axis of the contact carrier, the second slits having a second height y extending in the axial direction of the contact carrier, the second slits cooperating with the first slits to define a coil portion in the contact carrier therebetween which allows a current to flow and form an axial magnetic field along the axial direction of the contact carrier,
wherein assuming that the axial length of the contact carrier is 1, the first height x and the second height y satisfies a relationship given by the following expressions (1)-(3):
0.9xe2x89xa7xxe2x80x83xe2x80x83(1) 
xxe2x89xa7yxe2x89xa70.2xxe2x80x83xe2x80x83(2) 
1.4xe2x89xa7x+yxe2x89xa70.8xe2x80x83xe2x80x83(3) 